🏖️Case Study - Slapton Line Management Flashcards
What is the Slapton Line?
The fragile shingle bar which runs between Slapton Ley and the sea
Where is Slapton Sands?
Kingsbridge, South Devon, UK
Why is the shingle barrier under threat?
Erosion rates are increasing
Where are coastal management strategies installed around the area?
Slapton, Torcross and Beesands
How long is the shingle barrier?
7km
What defences are in place at Torcross?
A Sea wall
When was the sea wall at Torcross built?
1979
What happened to the Torcross sea wall in 2001?
It was partially destroyed by a storm and large amounts of sediment were washed away
What happened to the sea wall at Torcross in 2014?
The wall collapsed during a storm and the beach was built up again in order to protect it
What happened to the Slapton Line after the 2014 storm?
The worst affected section of the road was realigned
What length of the road was realigned in 2014?
200m
How much shingle was transported from the Strete Gate area to Slapton?
12,000 tonnes
What was created on the beach at Slapton for protection?
Shingle bastions
How effective were the shingle bastions?
Only for the short term, as up to 45% was washed away in a storm in 2008
What defences are in place at Beesands?
A sea wall and rock armour
When was the rock armour put in place at Beesands?
2016
How much rock was imported to build the Beesands rock armour?
2-4 tonnes
Why was the rock armour put in place at Beesands?
To try and stop the wall from being undercut and collapsing again
What happened to the Torcross sea wall in 2016?
It collapsed
How much was spent by the South Hams council on emergency flooding funding?
£250,000
How much did repairs to the wall in 2017 cost?
£2.4 million
How much steel and concrete was used to reinforce the wall?
710 tonnes of steel and 220m3 of concrete
How much shingle was washed away from Torcross in 2015?
27,000 tonnes in one night
How much did the shingle at Torcross cost?
£250,000
How much shingle was lost from the Slapton Line in the storms of 2000/2001?
5m from a 1000m stretch of beach
What was initially used to protect the road after the 2000/2001 storm?
3000 tonnes of rock armour, later removed due to damage to the SSSI
Why was Hallsands destroyed?
Due to dredging of shingle in the early 20th century from the sediment cell, which is virtually closed
What are the long term issues with these management strategies?
. May damage to vegetation
. If the barrier was breached, the Slapton Ley lagoon may be destroyed
. Expensive to maintain
How much sediment transport occurs on the beach at Slapton?
Next to none.
Processes: Evidence of deposition
Beesands beach
Processes: Evidence of transportation
Slapton Sands (barrier beach)
Processes: Evidence of erosion
Limpet Rocks (wave cut platform)
Dancing Beggars (stacks)
4 Examples of human interference
A379 (Kingsbridge to Dartmouth)
Car parks along the barrier beach
Start Bay Caravan Club Site
Defences
Defences: Length and age of sea wall at Torcross?
319m
1979, modified in 2000 by the Environment Agency
Defences: Height and age of sheet piling capped with concrete top just north of Torcross?
143m
1917
Defences: Length and age of Rock Revetment in front of a car park, north of Torcross?
795m
1979
Defences: What protects the more vulnerable parts of the A379?
Rock armour
Why was a report by Scott Wilson and the University of Plymouth commissioned in 2003?
Determine appropriate future shoreline management response
Look at impact of existing sea defences
Future Defences: Beach Nourishment Key Points
Import shingle- raise + widen beach, additional protection for road
£1.14 million every 10 years to maintain
Material from Isle of Wight, matches existing
RULED OUT
Future Defences: Shingle Recycling Key Points
Excavation of material from Strete Gate beach
Place on beach at Slapton
Raise + widen beach + protect road
Large environmental impact- disrupts geomorphology
£60,000, not guaranteed to work
RULED OUT
Future Defences: When might shingle recycling be used?
Useful on a small scale as a temporary solution
Future Defences: Road Realignment Key Points
Move A379 landwards
Proactive- before damage
Reactive- after storm
CHOSEN
Scored highest on tables
Sustainability: Why are the future defences considered to be sustainable?
Looked at from a social, economic and environmental angle
Sustainability: Why is it good that all strategies have been put on an open spreadsheet?
Constantly reviewed
Changed if any unexpected events
The sheet looks up to 2105, so is long term
Sustainability: Why was it good that stakeholders were consulted?
Experts, authorities and local people could talk, share lived experience and discuss their worries with the strategies
Sustainability: Why was the owner of Streete Gate beach useful in the discussion?
Lived experience from Hallsands following the large-scale shingle extraction
Why could it be argued the strategies aren’t sustainable?
Existing strategies aren’t being removed
January 2018, road destroyed, still not fixed
How many residential properties were at risk of coastal flooding?
48
What % of trade is passing?
50%
How much funding could be requested from the Environment Agency to coastal risk management activities over the next 20 years?
£1.78 million
What is the main challenge to coastal management?
Climate change
Who is the shoreline management organisation at Slapton?
Slapton Line Partnership
When was the SLP formed and why
. 2001
. After a storm damage a key road between Slapton and Street Gate
How much of the beach did the 2001 storm remove?
5m
What is the aim of the SLP
To promote a coordinated policy and ensure an appropriate contingency plan
What did the SLP decide to do?
Existing defences should be maintained over the next 20 years
What was it decided to do with the sea wall?
Maintain and improve it
How was the rock revetment repaired?
Through recovery and re profiling of the existing rock armour
Cost to repair the rock revetment
£10,000
What management was done to work with the natural process to increase beach size?
Beach recycling
How much did it cost to repair the sea wall?
£3 mill
How often do groynes need replacing?
Every 20-30 years
What is the main road in Slapton called?
A379
What is the long term recommendation for Slapton?
Continue a policy of Managed Realignment along the whole coast
How high is the risk to the shingle bank for the next 30-50 years?
Low
Energy at the coastline in Start Bay
Coastline has areas of both high and low energy with both erosion and depositional landforms
Where is the most heavenly managed areas and what do they have?
Torcross and Beesands which both have sea walls protected by rock armour
What happened in 2014?
Shingle bastions were built to try and reduce LSD and erosion but they were soon eroded
What happened in 2015
250,000 tonnes of shingle was moved from Street to Torcoss only to be washed away overnight in one winter storm
Why has rip-rap in North Hallsands been ineffective?
Large depletion of the beach as a natural defence
